Japanese Patent Laid-Open No. 10-270535 shows the structure of an alignment stage apparatus in a semiconductor exposure apparatus. FIG. 7 is a plan view of the alignment stage apparatus described in Japanese Patent Laid-Open No. 10-270535, and FIG. 8 is a side view of the same.
In the conventional alignment stage apparatus as shown in FIG. 7, coils 102 are arranged like a matrix in a base structure 101, and permanent magnets 112 are similarly arranged like a matrix under a movable stage main body 103. When a current is supplied to the driving coils 102 opposing the permanent magnets 112, the movable stage main body 103 receives a thrust by the Lorentz force and is driven.
An electrostatic chuck 106, which holds a wafer by the electrostatic force, and various types of sensors 104, e.g., a sensor for monitoring the light quantity of a light source and an alignment sensor, are arranged on the movable stage main body 103.
Bearings 107 for supporting the weight of the stage are arranged on the lower surface of the movable stage main body 103. The movable stage main body 103 is guided while sliding on the surface of the base structure 101 whose flatness is compensated for. Alternatively, the weight of the movable stage main body 103 can be supported by the Lorentz force. In this case, magnets are arranged on the lower surfaces of the bearings as well.
Two bar mirrors 105 are arranged on the movable stage main body 103 to be perpendicular to each other. A laser interferometer 108 mounted on an interferometer support 113 measures the position of the movable stage main body 103. A current is supplied to the driving coils 102 to align the movable stage main body 103 such that the measured position of the movable stage main body 103 coincides with a target value from a control device.
In the conventional stage structure shown in FIGS. 7 and 8, power feeding means 110 and power receiving means 109 are provided for supplying power to the electrostatic chuck 106, sensor 104, and the like, on the movable stage main body 103. The received power is stored in a rechargeable battery 111. As the power feeding means, for example, a method of mechanically bringing an electrical contact into contact, and a method of opposing electromagnetic cores 114 to each other to form a magnetic circuit and supplying power in a non-contact manner by electromagnetic induction, as shown in Japanese Patent Laid-Open No. 8-51137, are available.
FIG. 9 shows the schematic structure of the method of supplying power by electromagnetic induction. When an AC power supply 127 of several kHz to several tens of kHz is connected to the transmission side electromagnetic core, power is supplied to the reception side electromagnetic core by electromagnetic induction. The supplied power charges the battery 111.
In the conventional structure described above, when a movable stage returns to a wafer transfer position to transfer a wafer, the power feeding means and power receiving means oppose each other to charge the battery. In an exposure operation, or the like, during which the movable stage separates from the wafer transfer position, the power for the electrostatic chuck and sensors is supplied from the battery 111. After the exposure is complete, when the movable stage returns to the wafer transfer position again, the battery 111 is charged again.
According to Japanese Patent Laid-Open No. 8-51137, in a transport apparatus, which electrically chucks and transports a silicon wafer, a means for supplying power by electromagnetic induction is provided at each stop position along the transport path, so that the electrostatic chucking means is charged (for chucking) or discharged (for release). Although a capacitor for keeping the voltage is mounted, since power consumption for electrostatic chucking is very small, no battery is mounted.
In the conventional example described in Japanese Patent Laid-Open No. 10-270535, the power feeding means and power receiving means are provided for supplying power to the electrostatic chuck and sensors on the movable stage main body, as shown in FIG. 7. The received power is stored in the rechargeable battery. Therefore, power can be supplied only when the stage is located at a certain predetermined position, such as a wafer transfer position.
With this structure, since the power can only be supplied at a specific position, such as the wafer transfer position, the stage main body must be returned, when necessary, to a position where power can be supplied, to charge the battery. This prolongs the process interval of exposure, or the like, or interrupts the process, to accordingly decrease the throughput. The battery is charged after it is discharged to a certain degree, and it takes time to charge the battery. The alignment apparatus cannot start the next operation until charging is complete. This is disadvantageous in terms of throughput.
Also, in the conventional example described in Japanese Patent Laid-Open No. 8-51137, power can only be supplied at a specific position, such as a stop position, and, accordingly, cannot be supplied at an arbitrary position or timing. If a battery must be mounted on the movable stage from the viewpoint of power consumption in the movable stage, the same problems as those of the conventional example described in Japanese Patent Laid-Open No. 10-270535 arise.
Alternatively, no battery will be used and power may be supplied through an electrical cable. In this case, however, the accuracy of the movable stage is degraded by the disturbance of the cable. With a stage apparatus having a flat structure, it is difficult to arrange and package the cable. If the cable is rubbed, dust may be produced to attach to the wafer. If the jacket of the cable degrades, trouble, such as insufficient insulation or wire disconnection, may occur.